Device for limiting the number of revolution of a rotating shaft

ABSTRACT

A spline shaft rotatably driven by driving means meshes with two pinions having internally threaded bores engaging on two elongate members, partially screw threaded along their length, so that the pinions move along the elongate members in opposite directions upon rotation of the spline shaft. The pinions actuate stopping means after a certain number of revolutions of the spline shaft in a given direction. The elongate members are manually rotatable to adjust the starting positions of the pinions, and set the desired number of revolutions. Spring means urge the pinion towards the threaded parts of the elongated members if a pinion engages a non-threaded part of the member as a result of failure of the stopping means or over-adjustment of the starting position.

United States Patent [191 Mimeur 51 Feb. 27, 1973 DEVICE FOR LIMITINGTHE NUMBER OF REVOLUTION OF A ROTATING SHAFT Inventor: Robert Mimeur,Sallanches, France Assignee:

France Filed: Jan. 18, 1971 Appl. No.: 106,961

Foreign Application Priority Data Jan. 19, 1970 France ..7001743 US. Cl...192/l41, 200/47, 200/158, 192/143 Int. Cl ..Fl6d 71/00, I-I0lh 3/16Field of Search.....l92/l4l, 142 R, 143; 200/47, 200/158 ReferencesCited UNITED STATES PATENTS 4/1950 Lee 8/1925 Gofi' .11.": ..200/47 Ets.Carpano 8: Pons SA, Clauses,

Prim ary Examiner-Allan D. Herrmann Attorney-Robert E. Burns andEmmanuel J. Lobato [57] ABSTRACT A spline shaft rotatably driven bydriving means meshes with two pinions having internally threaded boresengaging on two elongate members, partially screw threaded along theirlength, so that the pinions move along the elongate members in oppositedirections upon rotation of the spline shaft. The pinions actuatestopping means after a certain number of revolutions of the spline shaftin a given direction. The elongate members are manually rotatable toadjust the starting positions of the pinions, and set the desired numberof revolutions. Spring means urge the pinion towards the threaded partsof the elongated members if a pinion engages a non-threaded part of themember as a result of failure of the stopping means or over-adjustmentof the starting position.

3 Claims, 2 Drawing Figures DEVICE FOR LIMITING THE NUMBER OF REVOLUTIONOF A ROTATING SHAFT BACKGROUND OF THE INVENTION The present inventionrelates to devices enabling limitation, at will and in the twodirections, of the number of turns made by a rotating shaft driven by anelectric motor in which the feed current is cut off when the requirednumber of turns has been reached.

Several devices for this purpose are known. These devices use either thetranslational movement of an index moved by means of a helicoidal, flator spiral cam, or the linear movement of one or more nuts along a screwthe rotation of which is related to the movement of the rotating shaft,or other means for the transformation of a rotary motion into linearmotion. In all of these types, a translationally moving member operates,at the end of its path in either direction, a control member which cutsoff the feed current to the motor.

These devices generally have two serious drawbacks. Firstly, any defectin the driving members causing the continued passage of feed currentwhen it should have been cut off inevitably causes destruction of ordamage to the device. Moreover, the device for manual adjustment of thepath of the translationally moving member is not visible in general andthe blind rotational adjustment of these members beyond certain limitsleads to incorrectly adjusted operation or damage to the device. Thesetwo drawbacks are particularly important if the mechanisms are operatedby persons who are not trained to carry out such delicate operations.

SUMMARY OF THE INVENTION The present invention aims to provide a devicein which prejudicial consequences due to failure of the control membersor incorrect manual operation are avoided, the translationally movingmembers being automatically uncoupled should they accidentally overrun apre-set value.

The device according to the invention comprises a translationally fixedby angularly rotatable spline shaft rotatably driven by a rotatableshaft, and which meshes with two pinions threadably engaging upon twoscrew threaded elongate members along which they can move in oppositedirection upon rotation of the spline shaft. According to the directionof rotation of the spline shaft, one or the other of the pinions movesto operate a fixed switch and thus cut off feed current to driving meansfor the shaft. In case the current is not switched off due to faultyoperation of the switch, the rotating pinion leaves the thread of thescrew with which is engaged, thus causing no damage. Means are providedso that the operator can turn the screw-threaded axes to regulate adesired number of turns any overrun of the maximum adjustment allowedcauses the pinion to disengage its screw without causing any damage.

DESCRIPTION OF A PREFERRED EMBODIMENT An embodiment of the inventionwill now be described by way of example, reference being made to theaccompanying drawings, in which:

FIG. 1 is schematic view of a device in a working position; and

FIG. 2 shows the device in a rest position.

As shown, the device comprises a spline shaft 1 rotatably supported on aframe of the device and driven by means of a rotatable shaft of anelectric motor 20 (shown schematically) and which meshes with twopinions 2 and 3. These pinions threadably engage, like two nuts, onscrews 4 and 5 respectively threaded with opposite hand threads..For onedirection of rotation of spline shaft 1, the pinion 2 moves towards theright, for example, whereas the pinion 3 moves towards the left.

The number of turns of the rotatable shaft in one direction is limitedby the distance between the respective pinions 2, 3 and a control pieceoperated thereby, 8 and 10 respectively. These two control piecesrespectively operate switches 12 and 13 fixed on a frame (not shown) ofthe device. The construction of the switches when the pinion 2 or 3 isfully screwed to the right hand side is such that the pressure of thecontrol pieces 8 or 10 on the push pieces 16 or 17 overcomes thepressure provided by springs 9 and 11 and cuts off a feed current, eachswitch controlling a particular direction of rotation of the shaft. Thescrews 4 and 5, are normally angularly fixed. However, they can beturned manually, for example by means of angle gears 6, l4 and 7, 15,the pinions 14 and 15 being rotatable from outside a casing enclosingthe device. It is thus possible to provide a manual variation of thedistance between each pinion 2 and 3 and their respective control piece8 and 10. In operation, starting with the mechanism in the position ofFIG. 1, and with the two switches 12 and 13 closed by the control pieces8 and 10 urged by springs 9 and 1 1, when the electric circuit is closedby the ope'rator, the electric motor starts and rotatably drives thespline shaft 1. The pinions 2 and 3 are then rotatably driven in thesame direction, which causes a translational movement of the pinions 2and 3 in opposite directions. For example, pinion 2 moves towards theright hand side of the drawing and pinion 3 towards the left. When thepinion 2 reaches the control piece 8, it moves it and thus switches offthe switch 12, which cuts the feed circuit and stops the device. Theoperator will therefore be unable to exceed the chosen number of turns.

When the machine is rotated in the opposite direction, the pinion 2moves towards the left and the pinion 3 towards the right. The latter,at the end of its path, moves the control piece 10 and cuts off theswitch 13. It is thus evident that the predetermined number of turns,corresponding to the translational motion of pinions 2 and 3, ispermanently maintained at its preregulated value set by manual operationof pinions l4 and 15.

If one of the switches, for example 12, does not work properly and doesnot cut the current at the right time, the pinion 2 will leave thethread of screw 4 and, urged by the spring 11, remain in that position,while the spline shaft and pinions continue to turn. There will hetherefore no damage to the device.

In the same way, as shown in FIG. 2, if the operator turns the screw 5by hand, through the gear 15, 7 so that the pinion 3 moves towards theleft of the drawing and leaves its thread, it will be disengaged fromits screw and able to turn freely, without creating any damage, simplycompressing the spring 19.

In the two cases, the simple reversal of rotation of the deviceautomatically reengages the uncoupled pinions on their respectivethreads.

The device according to the invention can be used in any situation wherean accurate adjustment of a whole or fractional number of turns made bya turning shaft is required. Instead of electric driving means, anyother commutative, mechanical, pneumatic, fluid, hydraulic or electronicmeans can be used, without departing from the scope of the invention.

A particular field of application for such devices is the accurate andpermanent adjustment of travel for blinds, sliding doors, roller blindsand other such devices, which are generally operated by unskilledpersons. Other fields of application of the device can be named, such asthe provision of precise alternating movement from a rotary movement,the programming of a machine tools as a function of the number of turnsof a shaft, or for mobile advertising panels.

What is claimed is:

1. In combination with a spline shaft rotatably driven by driving means,a device for controlling the driving means to limit the number of turnsof the spline shaft, comprising first and second elongate elementsparallel to said spline and screw threaded along a part of their lengthwith threads of opposite hand, first and second pinions havinginternally threaded bores engaging on said screw threaded elementsrespectively, said pinions meshing with said spline shaft so thatrotationof the spline shaft causes rotation of the pinions and movementthereof in opposite directions along the screw threaded parts of therespective elongate elements, and means for stopping said driving means,said stopping means being actuatable by one or the other of said pinionsupon movement of the pinions along the screw threaded part of therespective elongate elements.

2. A control device according to claim 1, comprising means for rotatingthe first and second elongate members whilst the driving means isstoppedto enable positional adjustment of the first and second pinionsrelative to the stopping means.

3. A control device according to claim 2, comprising means for urgingthe first and second pinions towards the threaded parts of the first andsecond elongate members when either one of the first and second pinionsengages on an unthreaded part of the respective one of the first andsecond elongate members as a result of failure of the stopping means orexcessive positional adjustment of the first and second pinions.

1. In combination with a spline shaft rotatably driven by driving means,a device for controlling the driving means to limit the number of turnsof the spline shaft, comprising first and second elongate elementsparallel to said spline and screw threaded along a part of their lengthwith threads of opposite hand, first and second pinions havinginternally threaded bores engaging on said screw threaded elementsrespectively, said pinions meshing with said spline shaft so thatrotation of the spline shaft causes rotation of the pinions and movementthereof in opposite directions along the screw threaded parts of therespective elongate elements, and means for stopping said driving means,said stopping means being actuatable by one or the other of said pinionsupon movement of the pinions along the screw threaded part of therespective elongate elements.
 2. A control device according to claim 1,comprising means for rotating the first and second elongate memberswhilst the driving means is stopped to enable positional adjustment ofthe first and second pinions relative to the stopping means.
 3. Acontrol device according to claim 2, comprising means for urging thefirst and second pinions towards the threaded parts of the first andsecond elongate members when either one of the first and second pinionsengages on an unthreaded part of the respective one of the first andsecond elongate members as a result of failure of the stopping means orexcessive positional adjustment of the first and second pinions.